Method of manufacturing fine metal powder and fine metal powder manufactured by using the same

ABSTRACT

There are disclosed a method of manufacturing fine metal powder and fine metal powder manufactured by using the same. The method of manufacturing fine metal powder includes forming a pattern having a predetermined size and shape on a base substrate, forming a metal film on the pattern, and separating the metal film from the pattern to obtain individual metal particles having a predetermined size and shape. The fine metal powder manufactured by the method has a uniform shape and a uniform particle size distribution. The fine metal powder is in the form of flakes, having a large ratio of particle diameter to thickness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.10-2010-0118172 filed on Nov. 25, 2010, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing fine metalpowder and fine metal powder manufactured by using the same, and moreparticularly, to a method of manufacturing fine metal powder in the formof flakes, having a uniform particle size distribution and fine metalpowder manufactured by using the same.

2. Description of the Related Art

As electronic products have become highly functional and miniaturized,various electronic components and materials used for the electronicproducts have rapidly become lighter and thinner, while also becomingshorter and smaller. In the case of a conductive electrode material,which is an essential material for forming electronic components andelectric circuits, the demand for electrode materials having superiorelectrode connectivity and conductivity, while allowing electrodes toremain thin, has been increasing.

In particular, an internal electrode used for a chip component requiringco-firing with a ceramic may have a defect, in that the electrodeconnectivity thereof may be deteriorated, depending on the level ofthinning and thickening of a ceramic layer. Due to a difference inshrinkage rates between the ceramic and the electrode material duringthe co-firing with the ceramic, the internal electrode may havelimitations, in that internal defects may be increased and electrodeconnectivity may be deteriorated, thereby leading to a degradation ofthe capacitance characteristics thereof.

Recently, in order to realize a high functional electronic component, anattempt to replace spherical metal powder which has been used as a mainintergradient of the conductive electrode material in the related art,with metal powder having the form of flakes has been proceeding. The useof the metal powder in the form of flakes is intended to improve thefunction of the electronic component by controlling the sinteringshrinkage rate of the electrode and the thinning of an internalelectrode layer.

The spherical metal powder has been manufactured by a wet method, avapor method, or the like. In particular, the spherical metal powderused for the electrode material has been manufactured by using a liquidreduction method, a hydrothermal method, an electrochemical method, achemical vapor deposition (CVD) method, a RF-plasma method or the like.

As metal powder particles have become finer, controlling the size andparticle size distribution thereof has increased in difficulty. Inaddition, in the case in which particulate metal powder is used as theelectrode material, a decrease in sintering temperature and rapidsintering shrinkage may occur during co-firing with a ceramic material.In order to solve these limitations, the method of dispersingparticulate ceramic powder capable of giving sintering delay within theelectrode, or coating the surfaces of metal particles has been reviewed.

In addition, as described above, when the metal powder in the form offlakes is used, an electrode layer may be thinner and electrodeconnectivity of the electrode may be improved.

The metal powder in the form of flakes is manufactured by a mechanicalgrinding method through a milling process. In the milling process, thespherical metal powder having a regular particle size distribution maybe modified to be metal powder in the form of flakes, by mechanicalenergy applied thereto. However, the metal powder in the form of flakesmanufactured by the milling process has a non-uniform shape and size andthere are limitations in forming a large aspect ratio thereof.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method of manufacturingfine metal powder in the form of flakes, having a uniform particle sizedistribution and fine metal powder manufactured by using the same.

According to an aspect of the present invention, there is provided amethod of manufacturing fine metal powder, including: forming a patternhaving a predetermined size and shape on a base substrate; forming ametal film on the pattern; and separating the metal film from thepattern to obtain individual metal particles having a predetermined sizeand shape.

The manufacturing method may further include forming a strip layer onthe pattern prior to the forming of the metal film.

The strip layer may be formed to have a thickness thicker than that ofthe metal film. The strip layer may be made of a material having lowreactivity with the metal film, without deforming the pattern of thebase substrate.

The strip layer may be formed of a polymeric material.

The separating of the metal film may be performed by removing the striplayer through the use of a solvent in which the strip layer is to bedissolved.

The manufacturing method may further include forming a strip layer onthe metal film and forming the metal film on the strip layer. Here, theforming of the strip layer and the forming of the metal film may beperformed once or more. The manufacturing method may further includeforming one or more other metal films on the metal film in order thatthe individual metal particles have a multilayer structure.

The manufacturing method may further include forming a metal oxide layeron the metal film in order that the individual metal particles have amultilayer structure.

The base substrate may be made of a glass or a polymeric material. Thepattern may be configured to have recess portions having a predeterminedsize and shape and projection portions having a predetermined size andshape.

The fine metal powder may be manufactured in such a manner as to allow aparticle size distribution thereof to be in the range of ±20% of a meanparticle diameter D₅₀.

The metal particles may have a ratio of particle diameter to thickness(particle diameter/thickness) in the range of 20 to 100.

According to another aspect of the present invention, there is providedfine metal powder, including metal particles having a predetermined sizeand shape, and having a particle size distribution in the range of ±20%of a mean particle diameter D₅₀.

The metal particles may have a ratio of particle diameter to thickness(particle diameter/thickness) in the range of 20 to 100.

The metal particles may have a particle diameter in the range of 1 to 10μm.

The metal particles may have a thickness in the range of 10 to 100 nm.

The metal particles may have a polygonal shape or a round shape.

The metal particles may have a multilayer structure in which a pluralityof metal layers are stacked.

The metal particles may have a multilayer structure in which a pluralityof metal layers and a plurality of metal oxide layers are stacked.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view schematically showing fine metal powderaccording to an exemplary embodiment of the present invention;

FIG. 2 is a scanning electron microphotograph (SEM) showing fine metalpowder according to an exemplary embodiment of the present invention;

FIG. 3 is a perspective view schematically showing fine metal powderaccording to another exemplary embodiment of the present invention;

FIG. 4 is a perspective view schematically showing fine metal powderaccording to another exemplary embodiment of the present invention;

FIG. 5A through FIG. 5C individually show a cross sectional view of aprocess for explaining a method of manufacturing fine metal powderaccording to an exemplary embodiment of the present invention; and

FIG. 6 shows a cross sectional view of a process for explaining a methodof manufacturing fine metal powder according to another exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings. The invention may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the shapes and sizes of elementsmay be exaggerated for clarity. Like reference numerals in the drawingsdenote like elements.

FIG. 1 is a perspective view schematically showing fine metal powderaccording to an exemplary embodiment of the present invention. FIG. 2 isa scanning electron microphotograph (SEM) showing fine metal powderaccording to the exemplary embodiment of the present invention.

Referring to FIG. 1 and FIG. 2, fine metal powder according to theexemplary embodiment may be formed of thin metal particles 30 in theform of flakes.

In the exemplary embodiment, the metal particles 30 are illustrated ashaving a rectangular shape. However, the present invention is notlimited thereto and the metal particles 30 may be formed to have variousshapes, for example, circular, polygonal, or the like.

According to the exemplary embodiment, the fine metal powder is formedby collecting the metal particles 30 having a predetermined size andshape. The metal particles forming the fine metal powder have a uniformshape and size. Amore detailed explanation with regard to this will bedescribed, in a method of manufacturing fine metal powder, to bedescribed later.

In the exemplary embodiment, a particle diameter w of metal particles 30may be 1 to 10 μm. The particle diameter of each metal particle 30 maybe based on the longest length of a surface thereof having a maximumsurface area.

The metal particles 30 may be in the form of flakes, having a largeratio of particle diameter w to thickness t. The ratio w/t of particlediameter to thickness may be 20 to 100. The thickness t of the metalparticles 30 may be 10 to 100 nm.

According to the present invention, the size of the metal particles maybe controlled, thereby allowing the particle size distribution of thefine metal powder to be uniformly performed. According to the exemplaryembodiment, the particle size distribution of the fine metal powder maybe in the range of ±20% of a mean particle diameter D₅₀. The meanparticle diameter D₅₀ of the fine metal powder may be 1 to 10 μm.

The fine metal powder according to the exemplary embodiment may be Ni,Cu, Ag, Au, Al or the like.

The fine metal powder according to the exemplary embodiment may be usedfor manufacturing a conductive paste. The conductive paste may be usedfor the wiring material of an electronic circuit, or for anelectromagnetic shielding material. In addition, the conductive pastemay be used for an internal electrode, in a multilayer ceramic capacitor(MLCC), a multilayer ceramic inductor, or the like.

The fine metal powder according to the exemplary embodiment may be inthe form of flakes, so that conductivity of the electrode using the finemetal powder may be not degraded and connectivity thereof may be higher.Moreover, when the fine metal powder is applied to an electroniccomponent requiring co-firing with a ceramic layer, a thin electrodelayer may be formed and sintering shrinkage may be controlled to therebyallowing the capacity of the electronic component to be secured.

FIG. 3 is a perspective view schematically showing fine metal powderaccording to another embodiment of the present invention. Differentcomponents from the above-mentioned embodiment will be explained infocus, and a detailed description about the same components will beomitted.

Referring to FIG. 3, the metal particles may have a multilayer structurein which a plurality of metal layers are stacked and include a firstmetal layer 31 and a second metal layer 32 stacked on the first metallayer 31.

FIG. 3 illustrates a structure in which two metal layers are stacked.However, the present invention is not limited thereto, and a structurein which two or more layers are stacked may be used.

The first metal layer 31 or the second metal layer 32 may be formed of ametal, such as Ni, Cu, Ag, Au, Al, or the like.

The first metal layer 31 and the second metal layer 32 may be formed ofdifferent metals. Each metal layer may be formed of an alloy includingone or more metals.

As aforementioned, the fine metal powder according to the exemplaryembodiment is formed by collecting the metal particles 30 having apredetermined size and shape. The metal particles forming the fine metalpowder have a uniform shape and size.

According to the exemplary embodiment, the particle size distribution ofthe fine metal powder may be in the range of ±20% of the mean particlediameter D₅₀. The mean particle diameter D₅₀ of the fine metal powdermay be 1 to 10 μm.

In the exemplary embodiment, the particle diameter of the metalparticles 30 may be 1 to 10 μm. Each thickness of the first metal layer31 and the second metal layer 32 may be 1 to 100 μm. The thicknesses ofthe first metal layer 31 and the second metal layer 32 may be adjusted,thereby allowing the ratio of particle diameter to thickness (particlediameter/thickness) of the metal particles to be adjusted. The ratio ofparticle diameter to thickness (particle diameter/thickness) of themetal particles may be 20 to 100.

FIG. 4 is a perspective view schematically showing fine metal powderaccording to another exemplary embodiment of the present invention.Different components from the above-mentioned embodiments will beexplained in focus, and a detailed description about the same componentswill be omitted.

Referring to FIG. 4, the metal particles 30 may have a multilayerstructure and include the first layer 31, a metal oxide layer 33 stackedon the first metal layer 31, and the second metal layer 32 stacked onthe metal oxide layer 33.

FIG. 4 illustrates a structure in which two metal layers and one metaloxide layer are stacked. However, the present invention is not limitedthereto, and a structure in which two metal layers and two or more metaloxide layers are stacked may be used. The order of stacking the metallayers and the metal oxide layer is not specifically limited. Themultilayer structure of the metal particles may be properly adjusteddepending on a required function.

As stated above, the first metal layer 31 or the second metal layer 32may be formed of a metal, such as Ni, Cu, Ag, Au, Al, or the like.

In the exemplary embodiment, the particle diameter of the metalparticles 30 may be 1 to 10 μm. Each thickness of the first metal layer31, the second metal layer 32, and the metal oxide layer 33 may be 10 to100 nm. The thicknesses of the first metal layer 31, the second metallayer 32, and the metal oxide layer 33 may be adjusted, thereby allowingthe ratio of particle diameter to thickness of the metal particles to beadjusted. The ratio of particle diameter to thickness (particlediameter/thickness) of the metal particles may be 20 to 100.

Hereafter, a method of manufacturing fine metal powder according to anexemplary embodiment of the present invention will be explained. Theconstitution of the fine metal powder will be also more clarified fromfollowing descriptions concerning the method of manufacturing the finemetal powder.

FIGS. 5A through 5C individually show a cross sectional view of aprocess for explaining a method of manufacturing fine metal powderaccording to an exemplary embodiment of the present invention.

First of all, a pattern P having a predetermined size and shape may beformed on a base substrate 10, as shown in FIG. 5A.

The base substrate 10 is not specifically limited, as long as it is amaterial facilitating the formation of the pattern. For example, a glassor polymeric material may be used as the base substrate.

As the polymeric material, polyethylene terephthalate (PET),polycarbonate (PC), polypropylene (PP), or the like may be used;however, the polymeric material is not limited thereto.

A method of forming the pattern P on the base substrate 10 is notspecifically limited and may be properly selected depending on thematerial of the base substrate. For example, optical lithography andphotolithography processes using a photosensitive resin may be used. Anano imprint Lithography (NIL) process using an ultraviolet curableresin or a thermosetting resin may be also used.

The pattern P may be formed on the base substrate by using a gravureprinting process, a chemical etching process, a mechanical machiningprocess, or the like.

In the exemplary embodiment, the pattern P of the base substrate isconfigured in such a manner that recess portions and projection portionsare alternatively disposed. According to the exemplary embodiment, eachof the recess portions and projection portions has a predetermined shapeand size. By using the upper surfaces of both of the recess portions andprojection portions, fine metal powder having a predetermined shape andsize may be manufactured.

In order to increase the manufacturing yield of the fine metal powder,the percentage of efficient pattern formation may be high. An efficientpattern refers to a portion, in which a metal film is formed, and thenthrough the subsequent separation of the metal film, metal particles areformed. In order to increase the percentage of efficient patternformation, a distance between effective patterns may be narrowed, or theeffective patterns may be formed as the recess portions and projectionportions as shown in the exemplary embodiment. Also, the patterns may beformed on the both surfaces of the base substrate.

Next, a strip layer 20 may be formed on the pattern P of the basesubstrate as shown in FIG. 5B.

Without forming the strip layer 20, a metal film 30 a may be formed onthe pattern P of the base substrate 10. However, in the case of formingthe strip layer 20, the metal film 30 a may be more easily separated.

The strip layer 20 is not specifically limited; however, it may beformed as a material having little or no reactivity with the metal film30 a, without deforming the pattern of the base substrate. In addition,the strip layer 20 may be formed as an easily removable material.

The strip layer 20 may be formed as the polymeric material; however, itis not limited thereto. As the polymeric material, a material easilyremovable in a specific solvent, for example, ethylcellulose or the likemay be used. However, the polymeric material is not limited thereto.

Ethylcellulose has a characteristic capable of easily dissolving insolvents, for example, alcohol, such as isopropyl alcohol (IPA) or thelike, and ketone, such as acetone, methyl ethyl ketone (MEK) or thelike.

In addition, the strip layer 20 may use a water soluble resin, such aspolyvinyl alcohol (PVA).

Moreover, the strip layer 20 may use a phenolic resins, such as apolyvinyl butyral (PVB), a polystyrene (PS), an acrylic resin, a novolacresin, or the like.

The strip layer 20 may be formed by applying a solution in which thepolymeric material is dissolved, to the base substrate. As the solventof the solution, a material which does not deform the pattern P formedon the base substrate 10, while easily dissolving the polymericmaterial, may be used.

In an exemplary embodiment of the present invention, a method of forminga polymeric solution may be properly selected according to the materialproperty of the polymeric solution or the shape and characteristic ofthe pattern P. For example, when the viscosity of the polymeric solutionis relatively low and the pattern P of the base substrate is formed tohave a small size, a spray coating method may be used; however, thepresent invention is not limited thereto. In this case, optimizednumerical values concerning variables, for example, the size, pressure,air pressure and the like of a spray nozzle, together with the dryingcharacteristic of the polymeric solution may be experimentally derived.Then, through the utilization of the optimized numerical values, thestrip layer 20 having a uniform thickness may be formed.

In addition, the formation of the strip layer 20 may be performed byusing various application methods, such a transfer type applicationmethod using a micro-gravure process, or a contact type applicationmethod using a bar-coater, a roller, or the like.

The thickness of the strip layer 20 may be properly adjusted dependingon the size of a metal particle to be manufactured. The thickness of thestrip layer may be thicker than that of the metal film 30 a to beformed.

For example, the thickness of the strip layer 20 may be 0.1 to 1 μm. Inthe case in which the thickness of the strip layer is too thin, theremoval of the strip layer may be difficult due to the difficulty ofsolvent penetration. In addition, in the case in which the thickness ofthe strip layer is too thick, an excessive amount of time and energy maybe consumed for the removal of the strip layer, thereby causing themetal film to be damaged.

Next, as shown in FIG. 5B, the metal film 30 a is formed on the striplayer 20.

A method of forming the metal film 30 a is not specifically limited, andthe forming of the metal film 30 a may be performed by a method wellknown in the art.

For example, a thermal evaporation method, an e-beam deposition method,or a physical vapor deposition method, such as a sputtering method orthe like may be used; however, the present invention is not limitedthereto.

In addition, after forming a metal seed layer on the strip layer 20 bythe sputtering method, the metal film 30 a having a desirable thicknessmay be formed by performing an electroplating process, based on thismetal seed layer. This electroplating process may be used to form athicker metal film.

In an exemplary embodiment of the present invention, the metal film 30 amay be formed to have a thickness of 10 to 100 nm.

Hereafter, the metal film is separated from the pattern of the basesubstrate, and individual metal particles having a predetermined sizeand shape corresponding to the shape and size of the pattern may beobtained. The obtaining of the metal particles may be performed by theremoval of the strip layer, and a detailed description thereof will beexplained later.

According to another embodiment of the present invention, the process offorming the metal film 30 a and the strip layer 20 may be performed oncemore, as shown in FIG. 5C. The method of forming the strip layer and themetal film is as aforementioned.

The number and order of the process of forming the metal film and thestrip layer are not specifically limited. When the process of formingthe metal film and the strip layer is repetitively performed, a greaternumber of metal particles may be manufactured at once.

According to an exemplary embodiment of the present invention, the metalfilm 30 a may be separated from the pattern P of the base substrate 10,thereby allowing the individual metal particles to be obtained. When thestrip layer is formed, the individual metal particles may be obtained byremoving the strip layer 20 formed between the base substrate 10 and themetal film 30 a.

More particularly, the strip layer 20 may be removed by using a specificsolvent capable of easily dissolving the strip layer 20.

For example, when ethylcellulose is used as the strip layer, theethylcellulose may exhibit superior solubility in ethanol, toluene, or amixed solvent thereof. Thus, when the base substrate is immersed in thissolvent, the strip layer 20 formed of the ethylcellulose may be easilydissolved, so that the metal film 30 a is separated therefrom, therebyallowing the individual metal particles 30 to be obtained, as shown inFIG. 1.

When the strip layer is not formed, the metal film is separated from thepattern of the base substrate, thereby allowing the individual metalparticles to be obtained.

According to the exemplary embodiment of the present invention, theindividual metal particles having a predetermined size and shapecorresponding to the shape and size of the pattern may be obtained. Inaddition, a plurality of metal particles having a uniform shape and sizemay be easily manufactured.

Moreover, since the shape and size of the pattern may be easilyadjusted, the metal particle may be easily manufactured according to adesigned shape and size.

FIG. 6 is a cross sectional view of a process for explaining a method ofmanufacturing fine metal powder according to another exemplaryembodiment of the present invention. Different components from theabove-mentioned embodiment will be explained in focus, and a detaileddescription about the same components will be omitted.

FIG. 6 may be understood as a process subsequent to FIG. 5B. The metalfilm 30 a shown in FIG. 5B may be understood as a first metal film 31 ain this exemplary embodiment. After forming the first metal film 31 a, asecond metal film 32 a may be formed on the first metal film 31 a. Amethod of forming the second metal film 32 a may use the above mentionedmethod of forming the metal film.

Moreover, while not illustrated, through the additional formation of oneor more metal films on the second metal film, the metal particles of amultilayer structure having two or more layers may be manufactured.

Hereafter, as mentioned above, the first metal film 31 a and the secondmetal film 32 a are separated from the pattern of the base substrate,thereby allowing the individual metal particles 30 having the firstmetal layer 31 and the second metal layer 32 to be obtained, as shown inFIG. 3.

Furthermore, while not illustrated, the metal oxide layer and the secondmetal film may be formed on the first metal film.

Hereafter, the first metal film and the second metal film are separatedfrom the pattern of the base substrate, so that the individual metalparticles 30 of the multilayer structure having the first metal layer31, the metal oxide layer 33 and the second metal layer 32 may beobtained, as shown in FIG. 4.

The number of repetition and the formation order of the metal film andthe metal oxide layer are not limited, and by adjusting these, themultilayer structure of the metal particles may be diversified.

The fine metal powder manufactured by the above methods may be variouslyused.

For example, the conductive paste may be manufactured by mixing the finemetal powder produced according to an exemplary embodiment of thepresent invention, a resin binder, and an organic solvent.

In this case, as the resin binder, an alkyd resin, ethylcellulose, orthe like, which is an organic compound easily removed during a firingprocess may be used. As the organic solvent, terpineol, butyl carbitolacetate, kerosene, or the like, which is an organic compound giving thepaste a proper viscosity and being easily volatilized by a dry treatmentafter being applied to a green sheet may be used.

The conductive paste manufactured in this manner may be used to form thewiring of the electronic circuit and the electrode of electronic devices(for example, MLCC, MLCI).

As set forth above, the fine metal powder according to exemplaryembodiments of the invention has a uniform shape and a uniform particlesize distribution. The fine metal powder is in the form of flakes,having a large ratio of particle diameter to thickness. Thus, when theconductive paste and the electromagnetic shielding material aremanufactured by using the fine metal powder, an electrode film havinghigh electrode connectivity may be formed. Accordingly, in themultilayer ceramic capacitor and the multilayer ceramic inductorrequiring the co-firing, an internal electrode thereof can be formedthinner. Moreover, the degradation of the electrode connectivity due tohigh temperature shrinkage may be minimized.

In the method of manufacturing fine metal powder according to exemplaryembodiments of the invention, the fine metal powder is formed by usingthe pattern so that the shape and size of the fine metal powder may beeasily controlled. Accordingly, metal powder having a specific shape canbe also manufactured.

In addition, by using the method of separating the individual metalparticles from the pattern, the size and shape of the metal particlesmay be uniformly formed, without causing the formation of a metalparticle cluster or agglomerate.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

1-13. (canceled)
 14. Fine metal powder comprising: metal particleshaving a predetermined size and shape, and having a particle sizedistribution in a range of ±20% of a mean particle diameter D₅₀.
 15. Thefine metal powder of claim 14, wherein the metal particles have a ratioof particle diameter to thickness (particle diameter/thickness) in arange of 20 to
 100. 16. The fine metal powder of claim 14, wherein themetal particles have a particle diameter in a range of 1 to 10 μm. 17.The fine metal powder of claim 14, wherein the metal particles have athickness in a range of 10 to 100 nm.
 18. The fine metal powder of claim14, wherein the metal particles have a polygonal shape or a round shape.19. The fine metal powder of claim 14, wherein the metal particles havea multilayer structure in which a plurality of metal layers are stacked.20. The fine metal powder of claim 14, wherein the metal particles havea multilayer structure in which a plurality of metal layers and aplurality of metal oxide layers are stacked.